Simeon Bogdanov

Electron spin contrast of Purcell-enhanced nitrogen-vacancy ensembles in nanodiamonds

Nitrogen-vacancy centers in diamond allow for coherent spin-state manipulation at room temperature, which could bring dramatic advances to nanoscale sensing and quantum information technology. We introduce a method for the optical measurement of the spin contrast in dense nitrogen-vacancy (NV) ensembles. This method brings insight into the interplay between the spin contrast and fluorescence lifetime. We show that for improving the spin readout sensitivity in NV ensembles, one should aim at modifying the far-field radiation pattern rather than enhancing the emission rate.

Ultrabright Room-Temperature Sub-Nanosecond Emission from Single Nitrogen-Vacancy Centers Coupled to Nanopatch Antennas

Solid-state quantum emitters are in high demand for emerging technologies such as advanced sensing and quantum information processing. Generally, these emitters are not sufficiently bright for practical applications, and a promising solution consists in coupling them to plasmonic nanostructures. Plasmonic nanostructures support broadband modes, making it possible to speed up the fluorescence emission in room-temperature emitters by several orders of magnitude. However, one has not yet achieved such a fluorescence lifetime shortening without a substantial loss in emission efficiency, largely because of strong absorption in metals and emitter bleaching. Here, we demonstrate ultrabright single-photon emission from photostable nitrogen-vacancy (NV) centers in nanodiamonds coupled to plasmonic nanocavities made of low-loss single-crystalline silver. We observe a 70-fold difference between the average fluorescence lifetimes and a 90-fold increase in the average detected saturated intensity. The nanocavity-coupled NVs produce up to 35 million photon counts per second, several times more than the previously reported rates from room-temperature quantum emitters.

Enhancement of Single-Photon Sources with Metamaterials

M. Y. Shalaginov, S. Bogdanov, V. V. Vorobyov, A. S. Lagutchev, A. V. Kildishev, A. V. Akimov, A. Boltasseva, and V. M. Shalaev1,∗ School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region,141700, Russia Russian Quantum Center, Skolkovo Innovation Center, Moscow Region, 143025, Russia Lebedev Physical Institute RAS, Moscow, 119991, Russia

Ultra-compact metallic interface for NV spin readout (Conference Presentation)

The spin-optical properties of nitrogen-vacancy (NV) centers in diamond have been demonstrated to enable a plethora of applications ranging from nanoscale sensing to quantum information technologies. The conventional design of NV-based devices requires separate infrastructures for delivering microwave (MW) excitation and guiding/collecting fluorescence signals. Typically, one fabricates dielectric waveguides or lenses next to metallic MW antennae. Here we showed that the device compactness can be substantially improved by the integration of NV centers with channel plasmonic waveguides milled in an optically thick metal layer that simultaneously acts as a MW antenna. The use of highly conductive plasmonic materials allows to fabricate monolithic ultra-compact structures supporting propagation of both MW and optical signals. We demonstrated optical readout of spin resonance by collecting channel plasmon polaritons scattered from the waveguide end.

Room-temperature high-speed control of quantum emitters with plasmonic nanostructures (Conference Presentation)

Plasmonic nanostructures offer a wide variety of optical modes that can be harnessed for controlling different radiation properties of single-photon emitters. These effects are broadband and are of special interest for quantum emitters at room temperature. We study these effects using nitrogen-vacancies in diamond nanocrystals. Extremely confined optical modes in hybrid cavity/nanoantenna structures lead to unprecedented levels of single-photon brightness at room temperature in the range of tens of million photons per second. Metamaterials offer highly broadband non-resonant brightness enhancement over 200 nm for all dipole orientations, which can be applied to emitters with broad spectrum or widely inhomogeneous line distributions. Dielectric bullseye corrugations on planar plasmonic films allow to reach highly directional Purcell enhanced emission within 5 degrees half-angle.

Spin readout of nitrogen-vacancy centers with plasmonic nanostructures (Conference Presentation)

Nitrogen-vacancy (NV) color centers in diamond possess electronic spins that one can manipulate coherently at room temperature using RF signals. The optical spin readout plays a key role in their performance for nanoscale magnetometry and quantum information processing. We demonstrate that plasmonic nanostructures can simultaneously guide optical, microwave and low-frequency signals ensuring spin manipulation and readout in an ultracompact setting. They can also enhance detected photon rates through efficient photon collection and shortening of the fluorescence lifetime. We show that in the case of dense NV ensembles the design of the optical readout interface must emphasize photon collection efficiency over Purcell enhancement. However, in the case of single NV centers, large Purcell enhancement may significantly improve the spin readout sensitivity. Enhancement for high-fidelity readout can be provided by nanoparticle-on-metal antennas featuring ultraconfined plasmonic modes.

Spin contrast of Purcell-enhanced nitrogen-vacancy centers in diamond

Nitrogen-vacancy centers in diamond allow coherent spin state manipulation and optical readout at room temperature, which has powerful applications in nanoscale sensing. Nanophotonic structures such as plasmonic waveguides, nanoantennae, metamaterials, and metasurfaces can enhance the detected fluorescence rate from such broadband emitters. The fluorescence of the coupled emitter is directed into confined plasmonic modes with high photonic density of states. However, an accurate spin readout requires both high photon counts and a strong contrast between the spin states, both of which can be influenced by the Purcell effect. We introduce a novel method for measuring the spin contrast in large nitrogen-vacancy ensembles. We use this method to study how the photonic density of states must be engineered in order to minimize the uncertainty of spin readout in dense NV ensembles. We describe these results using a kinetic model of the nitrogen-vacancys internal dynamics.

Patterning metamaterials for fast and efficient single-photon sources

Solid state quantum emitters are prime candidates to realize fast on-demand single-photon sources. The improvement in photon emission and collection efficiencies for quantum emitters, such as nitrogen-vacancy (NV) centers in diamond, can be achieved by using a near-field coupling to nanophotonic structures. Plasmonic metamaterial structures with hyperbolic dispersion have been previously demonstrated to significantly increase the fluorescence decay rates from NV centers. However, the electromagnetic waves propagating inside the metamaterial must be outcoupled before they succumb to ohmic losses. We propose a nano-grooved hyperbolic metamaterial that improves the collection efficiency from a nanodiamond-based NV center by a factor of 4.3 compared to the case of coupling to a flat metamaterial. Our design can be utilized to achieve highly efficient and fast single-photon sources based on a variety of quantum emitters.

Patterned multilayer metamaterial for fast and efficient photon collection from dipolar emitters

Solid-state quantum emitters are prime candidates for the realization of fast, on-demand single-photon sources. The improvement in photon emission rate and collection efficiency for point-like emitters can be achieved by using a near-field coupling to nanophotonic structures. Plasmonic metamaterials with hyperbolic dispersion have previously been demonstrated to significantly increase the fluorescence decay rates from dipolar emitters due to a large broadband density of plasmonic modes supported by such metamaterials. However, the emission coupled to the plasmonic modes must then be outcoupled into the far field before it succumbs to ohmic losses. We propose a nano-grooved hyperbolic metamaterial that improves the collection efficiency by several times compared to a conventional planar lamellar hyperbolic metamaterial. Our approach can be utilized to achieve broadband enhancement of emission for diverse types of quantum emitters.

Hyperbolic Metamaterials for Single-Photon Sources and Nanolasers

Hyperbolic metamaterials are anisotropic media that behave as metals or as dielectrics depending on light polarization. These plasmonic materials constitute a versatile platform for promoting both spontaneous and stimulated emission for a broad range of emitter wavelengths. We analyze experimental realizations of a single–photon source and of a plasmonic laser based on two different architectures of hyperbolic metamaterials. At the heart of this material capability lies the high broadband photonic density of states originating from a rich structure of confined plasmonic modes.